EF86 - Heater Current?

[Darkbluemurder]

Hi folks,

Yesterday I noticed that inspite of my library of tube amp books none carried a data sheet for the EF86. I am thinking of replacing one of the 12AX7s in my DR II with an EF86 and wondered whether this swap is safe as regards heater current.

Thanks for your help
Stephan

[cobalt]

Yes,

The EF86/6267 draws LESS heater current than the 12AX7, about .2A.
The plate and screen together(depending on voltage) draw about 4mA of B+.

cobalt
weirddave

[PRR]

> library of tube amp books

BOOKS!?

And I thought I was a caveman.

Use Franks:

http://www.mif.pg.gda.pl/homepages/frank/vs.html

> replacing one of the 12AX7s in my DR II with an EF86 and wondered ...heater current.

"In general", when a box has several big tubes and several small tubes, the load (B+ or heater) of the small tubes hardly matters, unless you increase the number of small tubes or add big tubes.

I would not be real concerned stuffing a 6DJ8 in a 12A_7 hole (rewired). The extra 0.065A vanishes in the overall 2+A drain. And as cobalt says: the EF86 is cooler than 12AX7.

[Darkbluemurder]

Thanks for the link, this is great info!
Cheers

[Happy k9]

On a related topic...

I recently picked up one of the new little 5W Blackheart heads to putz around with. The first thing I'm going to put in is a drop-in turret board from Mojo.

I've done basic amp and pedal mods, so I'm comfortable with doing mods that come with components and instructions, but I'm a bit soft on the math and science that goes into designing deeper mods...

Could someone explain to me what would be involved in converting the 12ax7 preamp section to an ef86 config?

Many thanks...

[Ears]

> library of tube amp books

BOOKS!?

And I thought I was a caveman.

Cool to have you back PRR, you must be taking a break from real engineering work!

Or has powerscaling forum recently absorbed your interest?.

Darkbluemurder and others.... check out and download Duncan Amps's tube data sheet locater . It has links directly to Frank's pages and other sources as necessary.

[skyboltone]

> library of tube amp books

BOOKS!?

And I thought I was a caveman.

Cool to have you back PRR, you must be taking a break from real engineering work!

Or has powerscaling forum recently absorbed your interest?.

Darkbluemurder and others.... check out and download Duncan Amps's tube data sheet locater . It has links directly to Frank's pages and other sources as necessary.

That's what I thought too. I miss the curmudgeonly cuss but check the date on the post. This is cyber resurrection

[dartanion]

On a related topic...

I recently picked up one of the new little 5W Blackheart heads to putz around with. The first thing I'm going to put in is a drop-in turret board from Mojo.

I've done basic amp and pedal mods, so I'm comfortable with doing mods that come with components and instructions, but I'm a bit soft on the math and science that goes into designing deeper mods...

Could someone explain to me what would be involved in converting the 12ax7 preamp section to an ef86 config?

Many thanks...

Download an AC30/6 schematic (or any other Vox with the EF86 channel) and copy the circuit from there. These will have the proper pinout and give you a good working EF86 channel. You can play with some of the values for different flavors too, but this is a good starting point. One issue that you'll face is that lack of a good supply of EF86s. They are very prone to being microphonic, so you'll need to weed through a bunch to find a good usable one.